EUCLID BEAMLABS LLC — Department of Energy SBIR Phase II: 11b

Description

In order to achieve sharp, high resolution real-time imaging, electron beams in a MeV UEM (ultrafast electron microscope) beamline need to minimize instabilities and energy spread during generation and acceleration. The stability of the normal conducting photocathode gun which is currently used to produce short electron bunches has been one of main elements limiting the further improvement of beam instability. The Superconducting RF (SRF) photocathode gun is a promising candidate to produce highly stable electrons for UEM/UED applications. It operates in an ultrahigh Q, CW mode, and dissipates a few watts of RF power, which make it possible to achieve a 10s ppm level of beam stability by using modern RF control techniques. Following the Phase II work plan, we have accomplished the engineering design of the conduction-cooled SRF cavity in all possible practical aspects. We have measured the QE of Nb and Nb3Sn. We have fabricated the cryostat and Nb cavity, and completed infrastructure work to install the Cryocooler. The cryocooler and the cryostat were integrated. Both the cool-down test (to 4K) and the magnetic shielding (<10 mG) test met our design targets. In close collaboration with Fermilab, the follow-up work of surface chemical processing, Q-slope test in the VTS (vertical test stand), Nb3Sn coating, etc., have been in preparation, in order to ensure the completion of all tasks before the end of Phase II. During the execution of our Phase II commercialization plan, we have worked closely with our collaborators at Brookhaven National Laboratory (BNL), who are also our customers. The location of the facility to host this SRF photogun and the future UED/UEM beamline has been identified in the evacuated ATF-II bunker (with UV laser beamline) at BNL. We had previously built and successfully tested an LLRF system for the Fermilab 1300-MHz conduction-cooled SRF cavities. During the execution of the Phase II Data Management Plan, the main results of Phase II were presented at multiple workshop and conferences. With the new opportunity provided by the SBIR Phase IIA program in 2021, we propose to improve and fully characterize this conduction-cooled, compact SRF CW MeV beam at BNL, and design and construct a UED beamline that eventually to become a user facility. The overall objective is that, by the end of Phase IIA, we will establish the world’s first high electron throughput (>10^11 e-/s) MeV UED/UEM facility at BNL. Similarly to Phase II, this Phase IIA project will be a joint effort, and the close collaboration remains strong between BNL and Euclid. The development of MeV-range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation in numbers of published DoE reports, which may lead to breakthroughs in fundamental science and applied technologies. The electron source we are proposing will significantly improve performance of the current MeV UEM.